This invention relates to an aluminosilicate zeolite (UZM4M) derived from an as synthesized zeolite designated UZM-4. The UZM-4 composition is structurally related to zeolite Q (BPH topology), but is often thermally stable up to a temperature of 600xc2x0 C. and has a higher Si/Al ratio in the range of about 1.5 to about 4.0.
Zeolites are crystalline aluminosilicate compositions which are microporous and which are formed from corner sharing AlO2 and SiO2 tetrahedra. Numerous zeolites, both naturally occurring and synthetically prepared are used in various industrial processes. Zeolites are characterized by having pore openings of uniform dimensions, having a significant ion exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without significantly displacing any atoms which make up the permanent zeolite crystal structure.
One particular zeolite, designated zeolite Q, was first disclosed in U.S. Pat. No. 2,991,151. The general formula for zeolite Q is represented in terms of mole ratio of the oxides by the following:
0.95xc2x10.05 M2/nO:Al2O3:2.2xc2x10.05 SiO2:xH2O 
where M designates at least one exchangeable cation, n represents the valence of M and x has a value from 0 to about 5. The examples in the patent are prepared with M being potassium. Synthesis of zeolite Q was conducted at 25xc2x0 C. to 50xc2x0 C. After activation at about 130xc2x0 C., zeolite Q was found to adsorb small polar molecules.
In a paper by John D. Sherman entitled, xe2x80x9cIdentification and Characterization of Zeolites Synthesized in the K2Oxe2x80x94Al2O3xe2x80x94SiO2xe2x80x94H2O System,xe2x80x9d Molecular Sievesxe2x80x94II(102) 30, 1974, he reports that the zeolite Q of the ""151 patent is the same zeolite as zeolite K-I reported by other researchers. Zeolite K-I was first reported by S. P. Zhdanov and M. E. Ovsepyon in Doklady Chemistry. Proc. Acad. Sci. USSR, 156, 756 (1964). M. E. Ovsepyan and S. P. Zhdanov further reported on K-I zeolite in Bull. Acad. Sci. USSR, Chem. Sci. 1, 8 (1965). R. M. Barrer et al. in J. Chem. Soc. (A) 2475 (1968) showed that K-I decomposed at 168xc2x0 C. It is also reported by Sherman and other researchers that zeolite Q is unstable above 130xc2x0 C. and is totally disintegrated at 200xc2x0 C. Owing to this thermal instability, zeolite Q has received little industrial interest. K. J. Andries et al., in Zeolites, 11, 124 (1991) proposed the BPH topology for zeolite Q. Synthesis of a pure form of zeolite Q was reported by K. J. Andries et al., in Zeolites, 11, 116 (1991). Finally, U.S. Pat. No. 5,382,420 discloses a composition designated ECR-33, which is a partially rare earth (La) exchanged zeolite Q. In all of the above reports, the Si/Al ratio is 1.
Copending application Ser. No. 09/705,653 filed Nov. 3, 2000 discloses the synthesis of a zeolite designated UZM-4, which appears to have a similar topology to that of zeolite Q, i.e., BPH, but has considerably different characteristics. The biggest difference is that UZM-4 has been synthesized with higher Si/Al ratios than zeolite Q, starting from a low of about 1.5 and going higher. The most important characteristic of UZM-4 is the greater thermal stability associated with the higher Si/Al ratios. UZM-4 in its various forms is stable to at least 400xc2x0 C. and often up to greater than 600xc2x0 C. The x-ray diffraction pattern of UZM-4 is noticeably different from that of zeolite-Q; and UZM-4 has smaller cell dimensions than that of zeolite Q, consistent with its higher Si/Al ratio.
Applicants have now modified the UZM-4 to give UZM-4M by treating it with a fluorosilicate salt and optionally following with a steaming, calcination, acid extraction, ion-exchange step, or a combination thereof. Skeels and Breck have disclosed in U.S. Pat. No. 4,610,856 a method for producing higher Si/Al ratio zeolites via silicon substitution for aluminum using an ammonium hexafluorosilicate post treatment. The method involves extraction of the Al from the zeolite framework, forming a defect that can be subsequently filled by Si, and producing (NH4)3AlF6 as a soluble by-product. The process is a delicate one since it is disclosed that the extraction of Al from the framework tends to be faster than the insertion of Si into the resulting defects, thereby putting the zeolite structure at risk if the number of defects gets too high. In this regard, the composition of the initial zeolite is very important. K. J. Andries et al. in Zeolites, 11, 116 (1991), applied the techniques of Skeels and Breck to Zeolite Q, attempting to raise the Si/Al ratio from 1 in Zeolite Q to targeted values of 1.35, 1.67, and 3. However, the experimentally obtained values were 1.26, 1.32, and destruction of the framework, respectively. Their conclusion was that the zeolite Q framework is very susceptible to destruction.
Starting with UZM4, applicants have successfully used fluorosilicate treatments and optionally steaming, calcination and ion-exchange steps or combinations of these, to generate a family of stable materials with a variety of pore and catalytic properties and with Si/Al ratios that range from about 1.75 to about 500 while retaining the BPH topology, all of which are designated UZM-4M.
As stated, the present invention relates to a new aluminosilicate zeolite designated UZM-4M. Accordingly, one embodiment of the invention is a microporous crystalline zeolite having a three-dimensional framework of at least AlO2 and SiO2 tetrahedral units and an empirical composition on an anhydrous basis expressed by an empirical formula of:
M1an+Al1-xExSiyOzxe2x80x83xe2x80x83(I) 
where M1 is at least one exchangeable cation selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals, hydronium ion, ammonium ion and mixtures thereof, xe2x80x9caxe2x80x9d is the mole ratio of M1 to (Al+E) and varies from about 0.15 to about 1.5, xe2x80x9cnxe2x80x9d is the weighted average valence of M1 and has a value of about 1 to about 3, E is an element selected from the group consisting of gallium, iron, boron, chromium, indium and mixtures thereof, xe2x80x9cxxe2x80x9d is the mole fraction of E and has a value from 0 to about 0.5, xe2x80x9cyxe2x80x9d is the mole ratio of Si to (Al+E) and varies from about 1.75 to about 500 and xe2x80x9czxe2x80x9d is the mole ratio of O to (Al+E) and has a value determined by the equation:
z=(axc2x7n+3+(4xc2x7y))/2 
and is characterized in that it has the x-ray diffraction pattern having at least the d-spacings and intensities set forth in Table A:
Another embodiment of the invention is a process for preparing the crystalline microporous zeolite described above. The process comprises treating a starting microporous crystalline zeolite with a fluorosilicate solution or slurry at a pH of about 3 to about 7, whereby framework aluminum atoms of the starting zeolite are removed and replaced by extraneous silicon atoms to give the modified zeolite; the starting zeolite having an empirical formula on an anhydrous basis of:
Mxe2x80x2mxe2x80x2n+Rrxe2x80x2p+Al1-xExSiyOzxe2x80x83xe2x80x83(III) 
where xe2x80x9cmxe2x80x2xe2x80x9d is the mole ratio of M to (Al+E) and varies from 0 to about 1.5, Mxe2x80x2 is at least one exchangeable cation selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals, hydrogen ion, ammonium ion and mixtures thereof, R is at least one organic cation selected from the group consisting of protonated amines, quaternary ammonium ions, diquaternary ammonium ions, protonated alkanolamines and quaternized alkanolammonium ions, xe2x80x9crxe2x80x2xe2x80x9d is the mole ratio of R to (Al+E) and has a value of 0 to about 1.5, xe2x80x9cpxe2x80x9d is the weighted average valence of R and has a value of about 1 to about 2, xe2x80x9cyxe2x80x9d is the ratio of Si to (Al+E) and varies from about 1.5 to about 4.0, E is an element selected from the group consisting of gallium, iron, chromium, indium, boron and mixtures thereof, xe2x80x9cxxe2x80x9d is the mole fraction of E and has a value from 0 to about 0.5 and xe2x80x9czxe2x80x9d is the mole ratio of 0 to (Al+E) and is given by the equation:
z=(mxc2x7n+rxc2x7p+3+4xc2x7y)/2. 
Yet another embodiment of the invention is the use of UZM-4M in a hydrocarbon process such as aromatic alkylation.
These and other objects and embodiments will become more apparent after a detailed description of the invention.